Captain Hammer (portrayed by Nathan Fillion) is the main antagonist who works against Dr. Horrible. Although he is rather unheroic, thoughtless, and self-centered, he is socially perceived as a superhero, and according to Horrible, is his nemesis.

Captain Hammer attempts to stop Dr. Horrible's Wonderflonium heist. Hammer damaged the remote control receiver that Dr. Horrible was using to control the courier van carrying the wonderflonium he needed for his Freeze Ray. The van went out of control and almost hit Penny. Hammer pushed her out of the way into a pile of garbage in an attempt to save her before trying to stop the van that was speeding towards her. Dr. Horrible, using his remote control, stopped the van but Hammer received the credit.

Hammer then takes Penny out on a date not long after. When he meets Billy in the laundromat, he reveals that he knows of his identity as Dr. Horrible and that he is only dating Penny in order to humiliate him. This prompts Dr. Horrible to decide to kill Hammer to enter the Evil League of Evil.

Hammer becomes known throughout the city for his opening of the new Caring Hands Homeless Shelter for Penny. During the opening of the new shelter Captain Hammer gives a speech which shows his utter disdain of the homeless as well as proclaiming the fact that he's slept with Penny with the audience still praising him and humiliating Penny. Before he finishes the last note of his song Dr. Horrible reveals himself and hits Hammer with his Freeze Ray. Dr. Horrible pauses for a moment before finishing him off with the Death Ray, and the Freeze Ray's effects wear off. Captain Hammer knocks him across the room with a punch to the face, damaging the Death Ray. Picking up the damaged Death Ray, Hammer decides to use it on Dr. Horrible himself, but upon firing the weapon, it explodes, sending him flying across the room and getting his first taste of physical pain, upon which he is instantaneously traumatized and runs off crying. The news then proclaims that Dr. Horrible has defeated Captain Hammer, who is last seen crying to a psychologist.

Superhuman Abilities

Captain Hammer has superhuman strength and is highly resistant to harm. He once threw an entire car at Horrible and frequently dislocates Horrible's shoulder. In fact, the exploding Death Ray was apparently the first thing to ever cause him pain.
He also refers to having a secret lair with equipment including a motorcycle and a "Hamjet." The "Hammer" part of his name is most likley believed by the public to refer to his fists, though he himself states that it instead refers to his penis. However, on a date with Penny, it appears he has a superhuman phobia of ducks, or that he doesn't like to get dirty seen from the last scene at the homeless kitchen.